Adversarial training (AT) is widely considered the state-of-the-art technique for improving the robustness of deep neural networks (DNNs) against adversarial examples (AEs). Nevertheless, recent studies have revealed that adversarially trained models are prone to unfairness problems. Recent works in this field usually apply class-wise regularization methods to enhance the fairness of AT. However, this paper discovers that these paradigms can be sub-optimal in improving robust fairness. Specifically, we empirically observe that the AEs that are already robust (referred to as “easy AEs” in this paper) are useless and even harmful in improving robust fairness. To this end, we propose the hard adversarial example mining (HAM) technique which concentrates on mining hard AEs while discarding the easy AEs in AT. Specifically, HAM identifies the easy AEs and hard AEs with a fast adversarial attack method. By discarding the easy AEs and reweighting the hard AEs, the robust fairness of the model can be efficiently and effectively improved. Extensive experimental results on four image classification datasets demonstrate the improvement of HAM in robust fairness and training efficiency compared to several state-of-the-art fair adversarial training methods. Our code is available athttps://github.com/yyl-github-1896/HAM.

Transfer-based adversarial attacks pose a severe threat to real-world deep learning systems since they do not require access to target models. Adversarial training (AT), which is recognized as the most effective defense against white-box attacks, also ensures high robustness against (black-box) transfer-based attacks. However, AT suffers from significant computational overhead because it repeatedly generates adversarial examples (AEs) throughout the entire training process. In this paper, we demonstrate that such repeated generation is unnecessary to achieve robustness against transfer-based attacks. Instead, pre-generating AEs all at once before training is sufficient, as proposed in our new defense paradigm called Data-Centric Robust Training (DCRT). DCRT employs clean data augmentation and adversarial data augmentation techniques to enhance the dataset before training. Our experimental results show that DCRT outperforms widely-used AT techniques (e.g., PGD-AT, TRADES, EAT, and FAT) in terms of transfer-based black-box robustness and even surpasses the top-1 defense on RobustBench when combined with common model-centric techniques. We also highlight additional benefits of DCRT, such as improved training efficiency and class-wise fairness.Our code will be available on GitHub.

Transferable adversarial examples cause practical security risks since they can mislead a target model without knowing its internal knowledge. A conventional recipe for maximizing transferability is to keep only the optimal adversarial example from all those obtained in the optimization pipeline. In this paper, for the first time, we revisit this convention and demonstrate that those discarded, sub-optimal adversarial examples can be reused to boost transferability. Specifically, we propose “Adversarial Example Soups” (AES), with AES-tune for averaging discarded adversarial examples in hyperparameter tuning and AES-rand for stability testing. In addition, our AES is inspired by “model soups”, which averages weights of multiple fine-tuned models for improved accuracy without increasing inference time. Extensive experiments validate the global effectiveness of our AES, boosting 10 state-of-the-art transfer attacks and their combinations by up to 13% against 10 diverse (defensive) target models. We also show the possibility of generalizing AES to other types, e.g., directly averaging multiple in-the-wild adversarial examples that yield comparable success. A promising byproduct of AES is the improved stealthiness of adversarial examples since the perturbation variances are naturally reduced.

State-of-the-art source code classification models exhibit excellent task transferability, in which the source code encoders are first pre-trained on a source domain dataset in a self-supervised manner and then fine-tuned on a supervised downstream dataset. Recent studies reveal that source code models are vulnerable to adversarial examples, which are crafted by applying semantic-preserving transformations that can mislead the prediction of the victim model. While existing research has introduced practical black-box adversarial attacks, these are often designed for transfer-based or query-based scenarios, necessitating access to the victim domain dataset or the query feedback of the victim system. These attack resources are very challenging or expensive to obtain in real-world situations. This paper proposes the cross-domain attack threat model against the transfer learning of source code where the adversary has only access to an open-sourced pre-trained code encoder. To achieve such realistic attacks, this paper designs the Code Transfer learning Adversarial Example (CodeTAE) method. CodeTAE applies various semantic-preserving transformations and utilizes a genetic algorithm to generate powerful identifiers, thereby enhancing the transferability of the generated adversarial examples. Experimental results on three code classification tasks show that the CodeTAE attack can achieve 30%$\sim ~80$% attack success rates under the cross-domain cross-architecture setting. Besides, the generated CodeTAE adversarial examples can be used in adversarial fine-tuning to enhance both the clean accuracy and the robustness of the code model. Our code is available athttps://github.com/yyl-github-1896/CodeTAE/.

Quantized neural networks (QNNs) have received increasing attention in resource-constrained scenarios due to their exceptional generalizability. However, their robustness against realistic black-box adversarial attacks has not been extensively studied. In this scenario, adversarial transferability is pursued across QNNs with different quantization bitwidths, which particularly involve unknown architectures and defense methods. Previous studies claim that transferability is difficult to achieve across QNNs with different bitwidths on the condition that they share the same architecture. However, we discover that under different architectures, transferability can be largely improved by using a QNN quantized with an extremely low bitwidth as the substitute model. We further improve the attack transferability by proposingquantization aware attack(QAA), which fine-tunes a QNN substitute model with a multiple-bitwidth training objective. In particular, we demonstrate that QAA addresses the two issues that are commonly known to hinder transferability: 1) quantization shifts and 2) gradient misalignments. Extensive experimental results validate the high transferability of the QAA to diverse target models. For instance, when adopting the ResNet-34 substitute model on ImageNet, QAA outperforms the current best attack in attacking standardly trained DNNs, adversarially trained DNNs, and QNNs with varied bitwidths by 4.6% ~ 20.9%, 8.8% ~ 13.4%, and 2.6% ~ 11.8% (absolute), respectively. In addition, QAA is efficient since it only takes one epoch for fine-tuning. In the end, we empirically explain the effectiveness of QAA from the view of the loss landscape. Our code is available at https://github.com/yyl-github-1896/QAA/.